Web-tensioning device

ABSTRACT

The disclosure embodies an elongated shoe for uniformly tensioning a web and includes mechanism for maintaining a preset shoe pressure over a range of web thicknesses. The shoe is pivotally mounted to press transversely downward under the influence of gravity upon a web to an extent permitted by an adjustable screw riding on the web and partially supporting the shoe.

United States Patent Shah [54] WEB-TENSIONING DEVICE [72] Inventor: Gautam C. Shah, Bombay, India [73] Assignee:

[22] Filed:

[21] Appl.No.:

Burroughs Corporation, Detroit, Mich.

Sept. 17, 1969 [52] US. Cl ..226/195, 188/651, 188/174,

242/752 [51] Int. Cl ..B65h 23/10 [58] Field of Search ..226/l95, 38, 39; 242/752,

[56] References Cited UNlT ED STATES PATENTS 3,494,527 2/1970 Baueretal 1 Mar. 7, 1972 Coker et a1. 242/752 3,386,635 6/1968 Nash ..226/195 X Primary Examiner-Richard A. Schacher Assistant Examiner-Gene A. Church Attorney-Paul W. Fish and Edwin W. Uren ABSTRACT The disclosure embodies an elongated shoe for uniformly tenstoning a web and includes mechanism for maintaining a preset shoe pressure over a range of web thicknesses. The

shoe is pivotally mounted to press transversely downward under the influence of gravity upon a web to an extent permitted by an adjustable screw riding on the web and partially I supporting the shoe.

2 Claims, 2 Drawing Figures .nnlllll ,mllllll H PATENTEDHAR H912 3.647. 128

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FIG. 2.

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' INVENTOR. GAUTAM C. SHAH.

WEB-TENSIONING DEVICE SUMMARY OF THE INVENTION The invention resides in the provision of an elongated shoe presettable to maintain uniformly distributed tension on webs of different thicknesses.

Prior art discloses web-tensioning devices, the drag or tension imparted by which being either fixed or manually adjustable. The normal force each exerts on a web is dependent on the web thickness. A constant normal force applied to webs of varying thickness can only be achieved by adjustable devices, and these must naturally be adjusted every time the web thickness is altered.

A typical web tensioning device has a relatively small effective area. To provide distributed drag or tension across a web requires the use of a plurality of such devices, resulting in commensurate increases in manufacturing and maintenance costs. The number of adjustments required each time the web thickness is changed is, of course, multiplied by the number of independent devices employed.

Previous web-tensioning devices generally employ resilient means to effect a normal force between the device and the web. The amplitude of this force is proportional to the amount of distortion of the resilient member. Webs of different thicknesses will distort the resilient member different amounts and will therefore be subjected to different forces from the device. Devices utilizing resilient means have the further disadvantage of being characteristically responsive to variations in ambient temperature and humidity, and their resilience usually decreases with age.

Accordingly, it is an object of this invention to provide a simple device which will automatically maintain a preset web tension on webs having a substantially wide range of thicknesses.

It is another object of this invention to provide a single device which will uniformly distribute tensioning forces across a web.

It is yet another object of this invention to provide a device which will furnish a tensioning force independent of ambient conditions and age.

IN THE DRAWINGS FIG. 1 is a side view of a web-tensioning device embodying features of the invention; and

FIG. 2 is a sectional view taken in the direction of the arrows 2-2 of FIG. 1.

Referring to FIGS. 1 and 2, the web-tensioning device shown has a support member or frame pivotally supporting an elongated shoe 12. An adjustable screw 14 (FIG. 2) is effectively positioned adjacent to the shoe l2 and limits the shoes rotation.

The frame 10 is formed by a horizontal baseplate 16 and two upright plates 18-18. The upright plates 1818 are parallel spaced and mounted on the baseplate 16. A holder 20 is pivotally mounted on a shaft 22 joumaled in the upright plates l8-18. As shown in FIG. 2, the shaft 22 passes through the holder 20 offset to the center of gravity of the holder 20.

An elongated and laterally curved semicylindrical shoe 12 is mounted on the holder 20. The upwardly curved edges of the shoe 12 are secured to the underside of the holder 20, and the axis of the shoe curvature is spaced from and parallel to the shaft 22. The curved portion of the shoe 12 extends downwardly toward the baseplate 16 from the holder 20 and may be transversely slotted to provide a plurality of commonly aligned and mounted shoe segments 24.

An internally threaded flange 26 (FIG. 2) is affixed to the edge of the holder 20 opposite to the edge being supported by the shaft 22 and central to the extremities of the holder 20. A screw 14 (FIG. 2) is threaded through the flange 26 (FIG. 2) and extends downwardly, adjacent to the shoe 12 and toward the base plate 16. The screw 14 (FIG. 2) has a smooth-surfaced contact head 28 at its downwardmost end. A locknut 29 secures the screw 14 against undesired rotation.

OPERATION With reference to FIGS. 1 and 2, assuming the device is in operation, a web 30, in being fed through the device, passes between the baseplate 16 and the shoe segments 24. The shoe segments press the web 30 against the baseplate 16 under the influence of gravity.

The combined weights of the holder 20, the shoe 12, the flange 26 (FIG. 2) and the screw 14 (FIG. 2) have three possible areas of support. The shaft 22 supports one edge of the holder 20. The remaining weight finds support at the area of contact between the shoe segments 24 and the web 30 and that between the screwhead 28 (FIG. 2) and the web 30. The weight supported by the shaft 22 remains relatively constant, but the remaining weight can be selectively apportioned between the screwhead 28 (FIG. 2) and the shoe segments 24. Since the screw 14 (FIG. 2) is threaded through the flange 26 (FIG. 2) affixed to the holder 20, it may be rotated in either direction to move it upward or downward with respect to the holder 20. Actually, as long as the screwhead 28 (FIG. 2) is in contact with the web 30, the screw itself remains vertically stationary and the holder 20 rotates about the shaft 22. This has the effect of raising and lowering the shoe segments 24 with respect to the web 30.

It should now be evident that the screw 14 (FIG. 2) may be rotated in one direction until the weight it shares with the shoe 12 bears entirely on the contact area between the shoe segments 24 and the web 30 or rotated in the other direction until this weight bears entirely on the contact area between the screwhead 28 (FIG. 2) and the web 30 or rotated to any intermediate position to establish a desired weight distribution. It should also be evident that, once set, this weight distribution will remain relatively constant over a substantial range of web thicknesses.

Iclaim:

l. A web-tensioning device comprising a supporting member, a shaft-supported holder pivotally mounted on said supporting member and gravitationally biased to rotate downwardly, an elongated and laterally curved semicylindrical shoe downwardly disposed from said holder to apply normal and frictional forces to a web, and a screw threaded downwardly through said holder adjacent to said shoe and rotatable to adjust the normal force applied to a web by said shoe.

2. The device as defined by claim I wherein said shoe is transversely slotted and is disposed in the direction of web motion from the pivot point of said holder.

4: e s a: s 

1. A web-tensioning device comprising a supporting member, a shaft-supported holder pivotally mounted on said supporting member and gravitationally biased to rotate downwardly, an elongated and laterally curved semicylindrical shoe downwardly disposed from said holder to apply normal and frictional forces to a web, and a screw threaded downwardly through said holder adjacent to said shoe and rotatable to adjust the normal force applied to a web by said shoe.
 2. The device as defined by claim 1 wherein said shoe is transversely slotted and is disposed in the direction of web motion from the pivot point of said holder. 